1. Field of the Invention
The present invention relates to vehicle lamps used as headlamps or auxiliary front lamps such as fog lamps. More particularly, it relates to vehicle lamps that are capable of emitting light that includes a component of the light directed in a lateral direction.
2. Description of the Related Art
One example of a related or conventional vehicle lamp capable of emitting light into a lateral direction is shown in FIG. 1A to FIG. 1C. In this specification, a front to back direction or a left to right direction refers to a corresponding direction viewed from a reference point, which is a headlamp mounted on a vehicle body. For example, “front”, “frontward”, or “forward” means the main illuminating direction or the direction of optical axis of a light source. And “side”, “sideward”, or “a lateral direction” means the right side of the vehicle when referring to a headlamp mounted on a right front side of a vehicle body.
The headlamp 90 shown in the drawing is the headlamp to be mounted on a right front side of a vehicle body. It includes a light source 92, a first reflecting surface 93, a projection lens 94, a shutter 95, a second reflecting surface 96, a third reflecting surface 97, a front lens 98, and an accessory 99. Reference numeral 100 denotes the vehicle body. The first reflecting surface 93 is constructed of, for example, an ellipsoidal reflecting surface having a first focus on the light source 92, and reflects light from the light source 92 toward front. The projection lens 94 converges direct light from the light source 92 and reflected light from the first reflecting surface 93 to a certain extent and emits light toward front. The shutter 95 is arranged near the focus of the projection lens 94 in the optical path (hereinafter referred to also as “main optical path”) of direct light from the light source 92 or reflected light from the first reflecting surface 93 to the projection lens 94, for blocking light to adjust the light distribution pattern.
The second reflecting surface 96 is constructed of an ellipsoidal reflecting surface. Its first focus is positioned on the light source 92. The longitudinal axis of the second reflecting surface 96 extends diagonally with respect to the main optical path, so that light emitted from the light source 92 to a forward and upward direction is reflected by the second reflecting surface 96 to a backward and downward direction.
The third reflecting surface 97 is constructed of a parabolic reflecting surface, and has its focus near the second focus of the second reflecting surface 96. In the illustrated example, the third reflecting surface 97 is made up of a compound reflector consisting of two reflecting portions 97a and 97b. The portion 97a on the left side of a vertical plane including the optical axis (right side in the drawing) reflects light reflected from the second reflecting surface 96 into a lateral direction. The portion 97b on the right side of the vertical plane passing trough the optical axis (left side in the drawing) reflects the light reflected from the second reflecting surface 96 into a middle region between the front and the side.
Light emitted from the light source 92 enters the projection lens 94 directly or indirectly via the first reflecting surface 93, where it is converged to a certain extent and emitted to the front. Part of the light to enter the projection lens 94 is blocked by the shutter 95, whereby a certain desired light distribution pattern is achieved in which no upward light beam is included, so as not to cause glare to an oncoming vehicle. This light illuminates a range denoted at L1 in FIG. 3, whereby a light beam known as a passing beam or a low beam is formed.
The forward and upward light from the light source 92, which will not be emitted from the projection lens 94 located in the front of the light source 92, is reflected by the second reflecting surface 96 and further reflected by the third reflecting surface 97. The light reflected by the left portion 97a of the third reflecting surface 97 is directed to the right side of the vehicle, and illuminates a range denoted at L2 in FIG. 3.
Meanwhile, the light reflected by the right portion 97b of the third reflecting surface 97 is directed to the middle region between the front and the right side and illuminates this middle region denoted at L3 in FIG. 3. The middle illumination range L3 extends across the front illumination range L1 and the right side illumination range L2 to provide smooth illuminance shift from the front illumination range L1 to the right side illumination range L2.
The vehicle lamp 90 thus illuminates both the front and the side of the vehicle with improved visibility in the moving direction of the vehicle when driving on a winding road or making a left or right turn, or a U-turn. The light distribution characteristics regarding the illumination range L1 are adjusted by means of the projection lens 94 and the shutter 95 so as to illuminate the front of the vehicle from near to far range.
The projection lens 94 alone cannot distribute light over a wide range as far as, for example, 90° in a left to right direction relative to an optical axis of the headlamp 90. Reflected light from the third reflecting surface 97 thus functions as supplementary light for illuminating a wider area than the illumination range L1 of the projection lens 4, i.e., it covers the illumination range L2 in the lateral direction and the illumination range L3 which is the middle region between the illumination ranges L1 and L2.
The optical system of this related art example has such settings that the illumination range L1 covers an area from 40° on the left to 40° on the right with respect to the front direction 0°, the illumination range L2 covers an area from 30° to 70° on the right, and the illumination range L3 covers an area from 20° to 50° on the right.
The front lens 98 of the vehicle lamp 90 extends over the whole light emitting region as shown in FIG. 1A. It covers and protects the inside, i.e., the light source 92, first reflecting surface 93, projection lens 94, shutter 95, second reflecting surface 96, and third reflecting surface 97. Thus, since the optical system of this related art example has a setting such that the portion 97a of the third reflecting surface 97 directs light into a range including a direction at 70° on the right side, the front lens 98 needs to extend over this lateral optical path.
Also, because of the need to secure this lateral optical path, there are limitations on the inside layout of the headlamp 90 or installation space of the accessory 99, which is usually fitted in this side portion of the headlamp 90.
That is, according to the construction of the related art example, the front lens 98 needs to be designed such as to extend largely to the side face of the vehicle, and the accessory 99 installed inside the headlamp 90 needs to be formed with a cutout portion 99a as shown in FIG. 2, i.e., there are large limitations on the design of the entire headlamp 90 including the front lens 98.
The optical system of this related art example is fixed such that the portion 97a of the third reflecting surface 97 directs light into a side range including a direction at 70° on the right. However, when turning, it is preferable that the visibility in the driving direction i.e., forward of the curve, is more brightly illuminated, rather than the side illumination. For example, when the vehicle turns to the left, it is preferable that the headlamp 90 mounted on the right front side of the vehicle body can illuminate the front, including the left front if possible, of the vehicle rather than the right side.